Which type of soil is most stable for road base support?

The most stable type of soil for road base support is granular soil. Granular soils, which include sand and gravel, are primarily composed of larger particles that can interlock, providing a solid and stable foundation for road construction. These types of soils have good drainage characteristics, which prevents water accumulation and reduces the risk of erosion, making them excellent for load-bearing applications like road bases.

Unlike cohesive soils, which are comprised of finer particles like clay, granular soils do not undergo significant volume changes with moisture variations, ensuring that they maintain their stability under load. Maintaining stability is critical for ensuring the longevity and safety of roadways, where the structural integrity is essential to support traffic loads and resist deformation over time.

Cohesive soils can exhibit high plasticity and can swell or shrink with moisture changes, which might lead to instability in the road construction context. Loose sand, while somewhat stable, lacks the necessary cohesion to support heavy loads effectively. Organic soils contain decomposed plant material, which can become compressible and unstable when wet, making them unsuitable for providing the necessary support for pavement structures.

Thus, granular soil stands out due to its advantageous physical properties that contribute to the strength and resilience required for reliable road base construction.